An airborne radar system may be used to search a volume of space for objects, to track detected objects, to identify certain objects, or to create an image of selected objects. In each case, accurate position knowledge of the radar's antenna may be critical to the quality of information gathered from the radar. Typically, the radar antenna's coordinate frame should be aligned with the Earth's coordinate frame. Misalignment of the antenna may result in incorrect location information about a detected object. In the case of an imaging radar, image artifacts such as shading or distortion can occur if the antenna's position is not accurately known.
According to some known techniques for aligning the antenna, special test equipment is used to mechanically align the antenna to the aircraft body coordinate frame. The test equipment, however, is typically expensive. Additionally, an Inertial Navigation System (INS) is usually employed to accurately determine the aircraft body coordinate frame orientation with respect to the Earth's coordinate frame. Accurate alignment of the INS sensor and the aircraft body coordinate frame must occur for accurate alignment of the radar antenna's coordinate frame to the Earth's coordinate frame. According to other known techniques, special test flights are performed to evaluate estimated alignments. Special test flights, however, may be expensive and time consuming. Furthermore, re-alignment of the antenna, the INS, or both may need to be performed when either system is replaced or repaired.